Greetings everyone
Using global app menu in xfce may be a little esoteric , appealling to those who whish a macos/unity , look and feel , so i just want to share the way i made it work for me , hoping it may be useful to anyone who wants to try it .

Step 1 . Install the plugin xfce4-topmenu-plugin , from synaptic with the necessary dependencies .
Step 2. Add to panel
Step 3. In the location /etc/profile.d ,create a text document named topmenu-gtk.sh ( so our full path will be /etc/profile.d/topmenu-gtk.sh) containing the following

Am I happy with it ? Well yes and no . I am happy because it works , but it does not follow panel transparency , you need to have an opaque panel . Also the plugin developer mentions , in his page two more plugins , one for qt applications and one for Firefox , but i was not able to locate them in the repos or in debian package pages .

Hope this post may help anyone who wants to use this plugin , and please add/correct , any other way you might have found on this